Little cites the theory of extraversion by Hans Eysenck and research by William Revelle of Northwestern University, explaining that introverts and extraverts naturally differ when it comes to their alertness and responsiveness to a given environment. A substance or scene that overstimulates the central nervous system of an introvert (which doesn't take much) might cause him or her to feel overwhelmed and exhausted, rather than excited and engaged.

In her 2012 TED Talk titled "The Power of Introverts," author Susan Cain reiterated this point in her definition of introversion, explaining that the trait is "different from being shy."

"Shyness is about fear of social judgment," Cain said. "Introversion is more about how do you respond to stimulation, including social stimulation. So extraverts really crave large amounts of stimulation, whereas introverts feel at their most alive and their most switched on and their most capable when they are in quieter, more low-key environments."

Now it goes without saying that most of our societal constructs cater to the former -- from open office spaces to loud bars to the structure of our educational system -- despite the fact that anywhere from one-third to half of the population has an introverted temperament.

While a person's introverted or extraverted tendencies fall within a spectrum -- there is no such thing as a pure introvert or pure extravert, according to famous Swiss psychiatrist Carl Jung -- an introvert is most obvious and vulnerable when he or she is in an overstimulating environment.

Coffee jitters aside, here are 10 ways introverts physically interact with the world around them differently than extraverts.

1. They withdraw in crowds."We hit the 20th century and we entered a new culture that historians call the culture of personality," said Cain in her TED Talk. "We had evolved from an agricultural economy to a world of big business, and so suddenly people are moving from small towns to the cities, and instead of working alongside people they've known all their lives, now they are having to prove themselves in a crowd of strangers."

The resulting crowd, which is often loud, noisy and congested, easily overstimulates introverts and drains them of their physical energy. They end up feeling more physically isolated than supported by their surroundings, and would rather be anywhere but that sea of people.

2. Small talk stresses them out, while deeper conversations make them feel alive.While most extraverts are energized by such interactions, introverts often feel intimidated, bored or exhausted by them. It's not uncommon in large conversations for introverts to take on the role of the quiet listener and then take time alone once it's complete. As Sophia Dembling, the author of The Introvert's Way: Living A Quiet Life In A Noisy World, explains in her book, it ultimately comes down to how a person receives (or doesn't receive) energy from his or her surroundings. Instead, introverts prefer deeper conversations, oftentimes about philosophical ideas.

3. They succeed on stage -- just not in the chit-chat afterwards.“At least half of people who speak for a living are introverted in nature,” according to Jennifer B. Kahnweiler, Ph.D, a certified speaking professional, executive coach and author of Quiet Influence: The Introvert’s Guide to Making a Difference. They simply play to their strengths, and prepare extensively. In fact, some of the most successful performers are introverts. Remaining on a stage, removed from a massive audience, proves far easier than the small talk-filled conversations that follow.

4. They get distracted easily, but rarely feel bored.If you're looking to destroy an introverted person's attention span, just put them in a situation where they feel overstimulated. Due to increased sensitivity to their surroundings, introverts struggle with feeling distracted and sometimes overwhelmed in large crowds and open office spaces.

However, when they are in peace and quiet, they have no issue tending to a favorite hobby or delving into a new book for hours. Having that time to take care of their inner selves helps them recharge while enjoying an activity they already enjoy.

5. They are naturally drawn to more creative, detail-oriented and solitary careers.Introverts naturally prefer spending time alone or in a small group, delving deeply into one task at a time and taking their time when it comes to making decisions and solving problems. Therefore, they fare better in work environments that allow them to do all of these things. Certain professions -- including writers,in-the-field natural scientists and behind-the-scenes tech workers -- can give introverts the intellectual stimulation they crave without the distracting environment they dislike.

6. When surrounded by people, they locate themselves close to an exit.Introverts not only feel physically uncomfortable in crowded places, but also do their best to mediate that discomfort by hanging as close to the periphery as possible. Whether it be by an exit, at the back of a concert hall, or an aisle row on an airplane, they avoid being surrounded by people on all sides, according to Dembling.

"We're likely to sit in places where we can get away when we're ready to -- easily," Dembling previously told HuffPost.

7. They think before they speak.This habit of introverts is often what earns them their reputations as listeners. It is second nature to them to take their time before opening their mouths, reflecting internally, instead of thinking out loud (which is more common among extraverts). They may seem more quiet and shy because of this behavior, but it just means that when they do speak, the words they share have that much more thought -- and sometimes power -- behind them.

8. They don't take on the mood of their environment like extraverts do.A 2013 study published in the journal Frontiers in Human Neuroscience found that extraverts and introverts process experiences through the brain's "reward" centers quite differently. While extraverts often sense a feel-good rush of dopamine related to their surroundings, introverts tend to not experience such a shift. In fact, people who are naturally introverted do not process rewards from external factors as strongly as extraverts do.

9. They physically can't stand talking on the phone.Most introverts screen their phone calls -- even from their friends -- for several reasons. The intrusive ringing forces them to abandon focus on a current project or thought and reassign it to something unexpected. Plus, most phone conversations require a certain level of small talk that introverts avoid. Instead, introverts may let calls go to voicemail so they can return them when they have the proper energy and attention to dedicate to the conversation.

10. They literally shut down when it's time to be alone."Solitude matters, and for some people, it is the air that they breathe." - Susan Cain

Every introvert has a limit when it comes to stimulation. HuffPost blogger Kate Bartolotta explains it well when she writes, "Think of each of us as having a cup of energy available. For introverts, most social interactions take a little out of that cup instead of filling it the way it does for extroverts. Most of us like it. We're happy to give, and love to see you. When the cup is empty though, we need some time to refuel."